Locking swivel devices are well known in the mechanical arts and are used in a wide variety of applications, such as medical device, sporting good, motor vehicle, and drilling applications. For example, during well drilling operations, a conventional locking swivel apparatus may be coupled to a drill string at the surface of the well (e.g., above the rotary table) with a portion of the drill string extending from the locking swivel downhole into the well bore. Locking the swivel couples the portion of the drill string disposed below the swivel to that disposed above (e.g., a side entry wire apparatus and/or an upper drive assembly), constraining them to rotate together about a longitudinal (usually cylindrical) axis. Unlocking the swivel allows the portion of the drill string disposed below the swivel to rotate about the longitudinal axis with respect to the portion disposed above the swivel.
U.S. Pat. No. 5,996,712 to Boyd discloses a Mechanical Locking Swivel Apparatus including an upper body portion having a counter bore for receiving the upper end of a mandrel, the mandrel being able to move within the counter bore. The upper end of the mandrel also includes a plurality of outwardly extending teeth. The upper body portion includes one or more pin members that extend into the counter bore and engage the teeth, thus locking the mandrel in place with respect to the upper body portion. The mandrel may be moved longitudinally in the counter bore thus disengaging the teeth from the pin members and allowing the mandrel to rotate freely about its longitudinal axis with respect to the upper body portion.
A mechanical locking swivel is also currently commercially available from Boyd's Rental Tools of New Iberia, La., and is the subject of co-pending U.S. patent application Ser. No. 09/498,188. In this commercially available tool, the upper body portion includes a plurality of teeth extending inward into the counter bore (rather than the pin members disclosed in the '712 patent). The teeth on the upper body portion slideably engage the teeth on the mandrel when the mandrel and upper body portion are pulled apart, thus locking the mandrel in place with the upper body portion. As described above with respect to the '712 patent, the mandrel may also be moved longitudinally in the counter bore towards the upper body portion, thus slideably disengaging the interlocking teeth and allowing the mandrel to rotate freely about its longitudinal axis with respect to the upper body portion.
While Boyd's commercially available locking swivel described above has shown itself to be highly serviceable, it is natural that repeated locking and unlocking (i.e., engaging and disengaging of the teeth disposed on the upper body portion and the mandrel) tends to cause wear and/or damage to the teeth. In time, if the teeth become sufficiently worn and/or damaged, replacement of either or both the mandrel and upper body portion is typically required at significant expense. It has also been found that there is a possibility for locking swivel apparatuses to unlock while being coupled to a drill string, thus increasing the difficulty of the coupling procedure. Therefore, there exists a need for a yet further improved locking swivel apparatus.